1. Field of the Invention
The present invention generally relates to optical disk apparatuses, and more particularly to an optical disk apparatus which detects a resolution of reproduced waves of signals recorded on an optical disk to automatically adjust the recording power.
2. Description of the Related Art
Memory media in the form of disks which are replayed by means of laser pickups of optical disk apparatuses are generally used as memory media which store information such as data bases and computer programs. The optical apparatuses include "read only type" apparatuses which can only read out information recorded on disks such as CDs (compact discs) and CD-ROMs, and "read and write type" apparatuses which can also write information on disks. The "read and write type" apparatuses include "write-once type" apparatuses (CD-R) which can write information only once and "erasable type" apparatuses which can write information any number of times such as magneto-optic disk (MO) apparatuses and phase change type disk (PD, CD-RW) apparatuses.
Since the conventional optical disk apparatuses are dedicated to any one of the above types of disks, it is necessary to have a plurality of optical disk apparatuses to replay the various types of disks. In order to avoid such an inconvenience, optical disk apparatuses have been developed which can replay different types of disks. One of such conventional optical disk apparatuses is an apparatus which has a disk cartridge mounted thereon containing CD-ROMs and PD disks.
Such optical disk apparatuses which can be used for both CD-ROMS and PD disks generally consist of an optical head, an optical system control part, a CD system signal processing part, a PD system signal processing part, and a motor driver. The optical head reads out information recorded on a disk or writes information on the disk. The optical system control part performs focus and tracking control of the optical head, drives a laser diode and control the output power thereof.
To replay a CD or a CD-ROM, signals which have been read out by the optical head are delivered to the CD system signal processing part via a signal system AGC amplifier. The CD system signal processing part performs signal processing such as EFM demodulation and error correction, with a spindle motor being CLV (Constant Linear Velocity) controlled by the motor driver to be actuated at a constant linear velocity.
To replay a PD disk, signals which have been read out by the optical head are delivered to the PD system signal processing part via the signal system AGC amplifier. The PD system signal processing part performs signal processing such as (2-7) demodulation and error correction. To record data on a PD disk, data signals to be written are subjected to signal processing such as (2-7) modulation. The data signals are then provided as recording signals to the optical system control part. When a PD is replayed or recorded, the spindle motor is ZCAV (Zone Constant Angular Velocity) controlled by the motor driver and a PD system CAV control circuit to rotate at a constant angular velocity.
In the optical disk apparatuses having the above construction, even if data is written to optical disks with the same recording power, resolutions of signals reproduced from each disk may change due to variations in the mechanical and electrical properties of the optical heads. For this reason, operations are conventionally carried out for determining an optimal value of a recording power of laser light which is emitted by the optical head and adjusting the recording power to the optimal value in an inspecting process after assembly of the apparatus.
The conventional operations for adjusting the recording power have been carried out in the following steps:
step 1: changing the recording power of laser light emitted from the optical head in a step-wise manner, and sequentially recording a signal with the different recording power; PA1 step 2: after the recording with the different recording power, reproducing the recorded signal and monitoring the reproduced signal by an oscilloscope; PA1 step 3: detecting a level of the recording power with which a predetermined resolution can be obtained, and storing the level as an optimal value of the recording power in a memory (EEPROM) of each drive; PA1 step 4: performing the above steps 1 through 3 on the most internal part and the most external part of a disk, and deriving linearly approximated values for the intermediate part from optimal values for the most internal and the most external parts.
However, since the above steps 1 through 4 have been conventionally carried out manually by operators, it takes a relatively long time to adjust the recording power to an optimal value, and in addition, the optimal value may fluctuate due to personal differences among the operators.
Further, although conventional optical disk apparatuses are shipped after the recording power has been adjusted to an optimal value by means of the above steps, the intensity of laser beams may decrease and thus the recording power may change due to secular changes (e.g., blur of lenses, adhesion of dusts to lenses, and deterioration in performance of the laser diode) after shipment of the apparatus. As a result, a possibility of error occurrence in reading or writing increases with the passage of time.